I am working on Interfacing Arduino with AD7150- a Capacitance to digital converter(CDC) chip from Manufacturers Analog Devices http://www.analog.com/static/imported-files/data_sheets/AD7150.pdf. This CDC chip is working on 3.3v and using Normal Arduino Dumi Works on 5V.
But when connect Arduino and CDC and run the i2c code... it finds the device in 0x48...
1.So,Is Now AD7150 is Connected with Arduino...Will it give data correctly...
2.Since 3v Part and 5V parts has different Voltage levels for HIGH and LOW... Is it correct to connect 3V and 5V part without logic level converter.
Previously my HMC 6352-compass module which is 3.3V part was worked correctly without
3.3V logic level converter
Some 3.3v devices can handle a 5v input (5 volt tolerant). Some can't. That device is not rated for 5v inputs. The datasheet is very specific that the maximum voltage applied to any input pin is the power supply +0.3v. That would be 3.6 volts in your case. It may last a while with more voltage than that on an input, or it may not.
I2C bus is a special gadget - it uses so called "open drain" (open collector) pin configuration on all devices hanging on the bus - therefore you need pull up resistors on SDA and SCL.
"Open drain" principle allows using an atmega powered 5V to be connected to devices powered by 3.3V (pullup resistors powered from 3.3V rail !).
When the 5V atmega's pins are NOT configured as "open drain" you may damage the 3V3 devices, unless you'll use a level translator..